Certain movements of the earth may be referred to in the art as “microseisms,” “microseismic disturbances,” and/or “microseismic perturbations.” For example, earth tremors (e.g., tectonic plate motion) such as those caused by natural phenomena (e.g., wind, ocean waves, earthquakes, etc.) may be considered to be microseisms. Further, man-made earth perturbations (e.g., perturbations caused by hydrofracturing, steam injection, carbon sequestration, etc.) may also be considered to be microseisms.
The technology to sense microseisms using fiber optic sensing systems is known. Fiber optic sensing systems are widely used for sensing disturbances (e.g., motion, acceleration, sound, etc.). Such fiber optic sensing systems often include a transducer for converting the disturbance into a phase change of light in an optical fiber.
Prior art transducers used to sense microseisms suffer from a number of deficiencies. For example, certain fiber optic sensing applications have spatial restrictions which limit the applicability of certain transducer designs. Further, the environment in which the transducers (and other optical elements of the fiber optic sensing systems) are used may require sensitivity and control not obtained or available from many conventional transducers. Further still, the operation of many optical transducers is adversely affected by disturbances along differing axes of motion.
Thus, it would be desirable to provide improved fiber optic transducers, and fiber optic accelerometers, and related fiber optic microseismic sensing systems to address these and other issues.